Whale Shark

The Whale Shark (Rhincodon typus) is the biggest fish in the sea, a charismatic marine megafauna that brings excitement and adventure to dive enthusiasts as supports thriving tourism industries in Ningaloo Marine Park in Australia, Belize, Philippines, Mexico, Seychelles, and Christmas Island.  Unfortunately, the planet's largest fish is on the verge of extinction. Whale sharks are extremely vulnerable to over exploitation by man for several reasons. They have a slow growth rate, only reaching maturity at around 30 years old and living as long as 60 - 100 years. Their reproduction rate is also very slow - long intervals between pregnancies and producing around a few hundred pups at one time. In Taiwan and India documented catches have declined from the 1980's to 2000's. In Indonesia, sightings of whale sharks have also declined significantly at sites including West Papua; North Sulawesi; North Kalimantan; Nusa Tenggara Timur; East Lombok; Bali; East Java, Karimunjawa Islands; Ciamis; Riau Islands; Aceh and Cenderawasih Bay. Few data are available on the exact time, the appearance, the size, numbers and behavior let alone the environmental factors (eg. tuna feeding, coral spawning, fish spawning) that may be causal factors to their appearance.

Based on the limited sources of information, in West Papua, local people find regular appearances of up to 4 whale sharks up to 10m in length almost all year round. These sharks are very tame and allow people to swim close while they consume fishes from fishponds. Other regular sightings of whale sharks have been recorded in waters between Indonesia and Australia. Various records showed that whale sharks made their appearances along the southern coast of West Java to the Timor Sea from January to October.

Ten individuals were recorded separately from 2002 to 2008 with sizes ranged from about 5m-12m in length. The appearance strengthens the hypothesis about the migration paths of whale sharks from Ningaloo in Australia and northeast towards southern Indonesian waters.  Some sources indicate that these sharks may make their way up north to Sulawesi and Kalimantan through the straits between islands of Java, Bali, Lombok, and Nusa Tenggara Timur. It may also be possible that the sharks migrate from Ningaloo in Australia via Sumatra, Indonesia and into the Indian Ocean. Whale shark sightings have also been recorded in other areas in central and northern Indonesia, namely the Karimunjawa Islands in the Java Sea, Northern Kalimantan, Anambas Island, and Weh Island in Aceh. Records on these sightings were mostly associated to feeding behavior as the sharks appeared in the waters where seasonal aggregation of shrimps or plankton form as well as spawning aggregation of various species of reef fish and migratory tuna stocks. Attention to the management of these sites is needed especially as reports from these sites are of whale sharks that have been captured dead, are landed by shark processors or eaten by the locals.

One of the most infamous whale sharks 'slaughters' occurred in the waters of Lembeh Strait, North Sulawesi from 1996 to1997. The international community were outraged and the media called the incident the “Manado Walls of Death” , where 18 whale sharks were caught by tiger mesh trap nets near the Tangkoko Nature Reserve, set up across the pelagic migratory channel by Taiwanese fishermen, together with 1424 manta rays, 789 marlin, 577 pilot whales, 257 dolphins, 84 green turtles, and 9 dugongs during a year of operation (http://darwin.bio.uci.edu/ ~sustain/bio65/indonesia/indon97e.htm). Anticipation and protective action were implored from the Indonesian government to stop the activity who then banned the net from being operated in Indonesia, thus to conserve whale shark, marine mammals, and sea turtles, endangered species under the Convention on Inbternational Trade of Endangered Species.

As part of the development of a marine protected area network in northern Aceh, Sumatra the WCS team is focusing on reports of whale shark sightings so that marine protected area planning will take their movements and behaviour into account. Sightings on Weh Island from 1990 to 1997 and from 2000 to 2008 during the months of September to April were of animals sized between 3 and 12 metres. There are some indications that in the 1990s, whale shark sightings were more frequent than the recent years of 2000s. As a preliminary study, this sighting information is basic to observations on whale shark ecology and movement in the region and may provide clues where these animals come from and where they travel to.

source : 

http://programs.wcs.org/indonesia/Wildlife/Whale-Shark.aspx